Method of manufacturing electromagnetic wave shielding plastic molding

Abstract

The present invention provides a method of manufacturing an electromagnetic wave shielding plastic molding, which comprises the step of, without prior washing and without providing a primer layer, or after providing a water-soluble primer layer, forming a conductive layer comprising at least one selected from the group consisting of Al, Cu, Ni, Cr and Sn and alloys thereof by high-frequency excited plasma. The electromagnetic wave shielding plastic molding thus-produced has excellent in electromagnetic wave shielding effects, adhering strength, humidity resistance and hardness, has economic advantages, and hence is useful as an electromagnetic wave shield for a plastic molding, such as the housing for a portable telephone.

What is claimed is: 
     
       1. A method of manufacturing an electromagnetic wave shielding plastic molding, which comprises the step of providing a conductive layer comprising at least a metal selected from the group consisting of Al, Cu, Ni, Cr and Sn or an alloy thereof on the surface of a plastic molding by high-frequency excited plasma in a vacuum chamber at a pressure or not more than 1×10 -3  Torr by the application of voltage from a high-frequency source, said conductive layer being formed on the plastic molding without prior washing and without providing a primer layer. 
     
     
       2. A method of manufacturing an electromagnetic wave shielding plastic molding as claimed in claim 1, wherein said conductive layer comprises a single layer or multiple layers. 
     
     
       3. A method of manufacturing an electromagnetic wave shielding plastic molding as claimed in claim 1, wherein after bombardment by high-frequency excited plasma, the conductive layer is provided by high-frequency excited plasma. 
     
     
       4. A method of manufacturing an electromagnetic wave shielding plastic molding as claimed in claim 1, wherein, without prior washing and without providing a primer coat layer, an aluminum film having a thickness of from 0.7 to 5.0 μm is formed by high-frequency excited plasma on the surface of the plastic molding. 
     
     
       5. A method of manufacturing an electromagnetic wave shielding plastic molding as claimed in claim 1, wherein, without prior washing and without providing a primer coat layer, a copper film having a thickness of from 0.7 to 5.0 μm and an aluminum film are formed by high-frequency excited plasma on the surface of the plastic molding. 
     
     
       6. A method of manufacturing an electromagnetic wave shielding plastic molding as claimed in claim 1 wherein, without prior washing and without providing a primer coat layer, a copper film having a thickness of 0.7 to 5.0 μm is formed in advance by high-frequency excited plasma in the same vacuum chamber on the surface of the plastic molding, and then a tin film having a thickness of from 0.05 to 2.0 μm is formed by high-frequency excited plasma. 
     
     
       7. A method of manufacturing an electromagnetic wave shielding plastic molding as claimed in claim 1 wherein, without prior washing and without providing a primer coat layer, a copper film having a thickness of from 0.7 to 5.0 μm is formed in advance by high-frequency excited plasma in the same vacuum chamber on the surface of the plastic molding, and then a nickel-chromium film having a thickness of from 0.05 to 2.0 μm and a nickel/chromium ratio of 50-80:50-20 is formed by high-frequency excited plasma. 
     
     
       8. A method of manufacturing an electromagnetic wave shielding plastic molding as claimed in claim 1 wherein, without prior washing and without providing a primer coat layer, a copper film having a thickness of from 0.7 to 5.0 μm is formed in advance by high-frequency excited plasma in the same vacuum chamber on the surface of the plastic molding, and then a metal or alloy film having a thickness of from 0.05 to 2.0 μm is formed in an organic gas atmosphere by high-frequency excited plasma. 
     
     
       9. A method of manufacturing an electromagnetic wave shielding plastic molding as claimed in claim 1 wherein, without prior washing and without providing a primer coat layer, a copper film having a thickness of from 0.7 to 5.0 μm is formed in advance by high-frequency excited plasma in the same vacuum chamber on the surface of the plastic molding, and then a conductive oxide film having a thickness of from 0.05 to 2.0 μm is formed by high-frequency excited plasma. 
     
     
       10. A method of manufacturing an electromagnetic wave shielding plastic molding as claimed in claim 1 wherein, without prior washing and without providing a primer coat layer, a copper film having a thickness of from 0.7 to 5.0 μm is formed in advance by high-frequency excited plasma in the same vacuum chamber on the surface of the plastic molding, and then a copper electrolytic plating film having a thickness of from 10 to 30 μm is formed. 
     
     
       11. A method of manufacturing an electromagnetic wave shielding plastic molding as claimed in claim 10, wherein a protecting film is formed on said copper electrolytic plating film. 
     
     
       12. A method of manufacturing an electromagnetic wave shielding plastic molding, which comprises the steps of providing a primer coat layer comprising a water-soluble paint on the surface of a plastic molding containing a filler, and after drying, providing a conductive layer comprising at least a metal selected from the group consisting of Al, Cu, Ni, Cr and Sn and alloys thereof by high-frequency excited plasma in a vacuum chamber at a pressure of not more than 1×10 -3  Torr by the application of voltage from a high-frequency source. 
     
     
       13. A method of manufacturing an electromagnetic wave shielding plastic molding as claimed in claim 12, wherein said conductive layer comprises a single layer or multiple films. 
     
     
       14. A method of manufacturing an electromagnetic wave shielding plastic molding as claimed in claim 12, wherein a primer coat layer comprising a water-soluble paint and having a thickness of from 1 to 30 μm is formed on the surface of the plastic molding containing a filler, and after low-temperature drying at a temperature of up to 100° C. an aluminum film having a thickness of from 0.6 to 5.0 μm is formed by high-frequency excited plasma in said vacuum chamber. 
     
     
       15. A method of manufacturing an electromagnetic wave shielding plastic molding as claimed in claim 14 wherein, a primer coat layer comprising a water-soluble paint and having a thickness of from 1 to 30 μm is formed on the surface of the plastic molding containing a filler, then after low-temperature drying at a temperature of up to 100° C., a copper film having a thickness of from 0.7 to 5.0 μm is formed in advance by high-frequency excited plasma in the vacuum chamber at a pressure of not more than 1×10 -3  Torr, and a corrosion-resistant metal or alloy film having a thickness of from 0.05 to 3.0 μm is further formed. 
     
     
       16. A method of manufacturing an electromagnetic wave shielding plastic molding as claimed in claim 15, wherein said corrosion-resistant metal or alloy film is formed in an organic gas atmosphere. 
     
     
       17. A method of manufacturing an electromagnetic wave shielding plastic molding, which comprises the steps of previously washing parts of surface of a plastic molding, which are contacted by molding pins or sliding cores adhering a sliding oil at the surface thereof, using an organic solvent or organic solvents, followed by bombard-treating the surface of plastic molding with high-frequency plasma, and then providing a conductive layer comprising at least one selected from the group consisting of Al, Cu, Ni, Cr and Sn and alloys thereof by high-frequency excited plasma on the surface of a plastic molding at a pressure of not more than 1×10 -3  Torr by the application of voltage from a high-frequency source. 
     
     
       18. A method as claimed in claim 17, wherein the organic solvent has a low boiling points. 
     
     
       19. A method as claimed in claim 18, wherein the organic solvent is selected from the group of ethanol, n-hexane and diethyl ether.